Actually, the number order is reversed. The 12G206 heads are pretty much a USA only type head from the early 1098's. The 12G295 heads are the later heads. These are often referred to as the Cooper heads for small bore engines. The only drawback on the 12G295 heads is that the factory did such a good job putting the new intake port in the 295 casting that the valves have very little maintenance margin for the valve seats. The 1.218" stock intake valve for the 295 head is left with very little seat after recutting. Look closely at the 295 intake port and it resembles the 1275 quite a bit.
If a machine shop is contracted to do a valve job, they better not be "ham-fisted" with the cutting stone tool. The seats will just fall away and you'll be left with a very pocketed head or their excuses or a request to put intake valve seats in the head for which they'll pick the wrong ones and you'll end up with a mess on your hands.
The 206 head casting usually has the 1.156" intakes in it. A good head for 948's. But for 1098,'s it is a great candidate to have the 1.218" intakes transferred over and a good 3-angle valve job and mild port cleanup done.
Both the 206 and 295 heads use the 1.00" exhaust valve head diameter.
HTH,
Mike Miller